What's the terrain like for this? Is it like a trail run (dirt, small rocks, grass, etc), or are there some rocks you'd have to scale?

I did the 10K last spring, at Algonkian (that's the DC area one). I was not impressed with the course. A lot of it was narrow, with the earlier heats returning in the opposite direction on the looped course. This meant you couldn't pass anyone for a good chunk of time (very frustrating if you're trying to get a PR!).

Also, I confirmed with another friend who did the 10K in a faster heat than me: The course just smelled WEIRD. Like sewage. He & I both agreed we would not be signing up again.

That said, there are a couple of pros: The party after area was nice. I enjoyed my free beer. The music was fun, and there were a lot of free samples of Clif Blox and other goo.

Anyone do one of their races before? Anyone signed up for it in the Spring?